This invention relates to an environmentally controlled cartridge for protecting data storage media therein and to a method for controlling the internal cartridge environment.
Many organizations have long term data storage requirements. Typically, these requirements are addressed by storing important data on media such as magnetic tapes. As those skilled in the art will recognize, however, functional lifetimes of magnetic tape as well as other types of data storage media (disk, tape, optical, magnetic, etc.) are highly sensitive to environmental conditions and, in particular, humidity, airborne pollutants and particulates.
The lifetime of data storage media is generally defined as the length of time it may be archived until data can no longer be read back at the originally specified performance levels. For example, properly manufactured metal particle (MP) tapes operated and stored under controlled conditions can have a life expectancy exceeding 50 years. Such conditions require, however, low controlled humidity on the order of 20-30%. With moderate humidity (50%), the functional lifetime of an MP tape can be reduced to two years. But with elevated humidity (80%) the lifetime can be reduced to one month or less. Typical failure modes include hydrolytic degradation of the binder (xe2x80x9csticky tapexe2x80x9d), reductions in binder adhesion, irreversible substrate shrinkage and loss of magnetic remanence or coercivity (signal loss).
In a further example, FIG. 6 illustrates the relationship between humidity and temperature and the resultant effects on the stability and life of Metal Evaporated (ME) tapes. As shown therein, with temperatures in the approximate range of 16xc2x0 C. to 32xc2x0 C., humidity strongly influences the lifetime of the media. With an elevated specific humidity (i.e.  greater than 0.013), tape instability is experienced. With a moderate level of specific humidity (i.e. 0.08 greater than x greater than 0.013), the optimum operating environment is achieved. Where the specific humidity levels are less than 0.08, high tape wear and low output is experienced. Metal Evaporated (ME) type media has an optimal environmental operating zone requiring a moderate humidity from 40-70% (specific humidity, 0.08 greater than x greater than 0.013).
In the case of the specific humidity requirements of magnetic tapes, the primary options for users to ensure long term data integrity and reliable tape operation have heretofore been to use environmentally controlled tape storage vaults, frequent replacement of tapes or migration of data to new media types. Regardless of the approach, preservation of stored data requires regular media sampling and migration procedures. It is not unusual for large data storage users to perform data migration and/or tape replacement every 3-5 years to insure the integrity of their data; such procedures are costly and can be disruptive to operations.
Humidity is also known to affect magnetic disk media operation as well. For example, the tribology between the head and disk is significantly affected by the relative humidity of the disk/head environment. In broad terms, a very low relative humidity results in poor start-stop tribology and therefore poor reliability. On the other hand, excessive relative humidity contributes to excessive sticking force, when the head is stationary on the disk. Excessive sticking force results in possibly damage to head or suspension components. These problems have motivated the development of environmental control schemes for fixed disk (sealed) magnetic disk drives.
Examples of magnetic disk drive environmental controls are shown in U.S. Pat. No. 4,620,248 issued to Gitzendanner and U.S. Pat. No. 4,863,499 issued to Osendorf. In these patents, the environment of a sealed magnetic disk drive is humidity controlled by utilizing a desiccant. The ingestion of airborne contaminants and particulates during the disk drive""s temperature and elevation cycling is minimized by incorporating filter and getter functions into a breather assembly. Unlike the disk media within a sealed disk drive, data storage media such as magnetic tape is exposed to the outside environment during every use. Although this media is housed within a cartridge, the cartridge is opened to permit the drive""s access to the media. In addition, the cartridge due to its design does not environmentally protect the tape when removed from the drive.
Consequently, a need has developed for an environmentally controlled data storage media cartridge and a method of controlling the internal environment of the cartridge.
It is a principal object of the present invention to control the humidity levels inside a cartridge for an extended period of time by providing a system which selectively exposes a charged desiccant to data storage media in response to the insertion and removal of the cartridge from a drive.
It is also an objective of the invention to seal the cartridge to reduce external-to-internal/internal-to-external air leakage rates to an acceptable level consistent with the desired life of the charged desiccant.
It is another objective of the invention to balance air pressure between the inside of the closed cartridge and the external environment to protect the integrity of the aforementioned seal over temperature and air pressure variations.
It is yet another object of the invention to provide a cartridge structure and method to maintain an internal cartridge environment free of chemical and particulate pollutants for the data storage media in the cartridge.
It is still another object of the invention to increase the lifetime of desiccant inside a variety of cartridges.
It is yet another object of the invention to selectively expose media to desiccant that is stored within the cartridge.
In carrying out the above objects and other objects and features, an environmentally controlled cartridge for protecting data storage media from disallowed humidity levels, airborne chemical contaminants and particulate levels is provided. The cartridge includes a first chamber that is normally sealed but openable to ambient and adapted to contain data storage media; a second chamber adapted to communicate with means to control moisture and chemical pollutants in the first chamber; and means to communicate between the first chamber and the second chamber when the first chamber is open to the ambient environment.
In a preferred embodiment, the communication means comprises an opening between the first and second chambers and the humidity control means and/or chemical pollutant getter means that are in communication with and preferably, but not necessarily, disposed inside of the second chamber. A seal is moveably affixable to the opening of the second chamber. An actuator is connected to the seal to close the second chamber""s opening when the first chamber is open. When the cartridge is inserted into a compatible drive and media access is required, the first chamber is opened. Depending upon the specific cartridge requirements, the first chamber""s sealable opening element may consist of a pivoting, sliding, rotating, removable section or the like. The seal actuator links the opening element of the first chamber to the seal of the second. Alternatively, the seal actuator links cartridge insertion detection means (independent of the opening elements of the first chamber) and the second chamber seal. A breather opening is provided in the exterior wall of the first chamber. While the cartridge is sealed, desiccant is exposed to the data storage media and internal cartridge air in order to maintain required humidity levels. Likewise, the pollutant getter material is exposed the data storage media and the internal cartridge air for the purpose of absorbing airborne chemical pollutants.
The second chamber""s moveably affixable seal may utilize a variety of methods to efficiently allow for the air exchange between the first chamber and the second when the seal is open. Embodiments can include the use of pivoting, sliding or rotating elementsxe2x80x94all with linkages to the first chamber""s sealable opening to selectively seal the chambers from one another. In the closed position, the seal functions to prevent the flow of air between the chambers.
In a preferred embodiment, the breather may comprise a breather filter affixable to the breather opening to prevent particulates from entering the cartridge, and a pollutant getter also affixable to the breather opening to trap airborne chemical pollutants and prevent them from entering the cartridge. This breather is one component of the entire cartridge system which controls the interior environment of the cartridge. The breather opening is of an area and length to maintain a balance in pressure between the interior and exterior of the cartridge while preventing the passage of moist air into or out of the cartridge. The breather thereby protects the integrity of the cartridge seals without compromising the effectiveness of the desiccant. The particulars of breather design are well known in the art.
Also in a preferred embodiment, the cartridge for protecting data storage media may include a cartridge having exterior walls about a first chamber openable to the ambient environment and adapted to contain data storage media and a second chamber having an opening to the first chamber; a pollutant getter disposed inside of the second chamber; a charged desiccant disposed within the second chamber, the charged desiccant operative to provide a constant humidity level for the internal cartridge air; a seal moveably affixable to the opening of the second chamber; an actuator connected to the seal; a breather; a breather filter; a breather pollutant getter; and cartridge seal(s) disposed around openings in the first chamber used by the drive to gain access to the media as well as between the individual components of the cartridge case itself. Taken together, these seals serve to reduce the flow of air between the external environment and the internal cartridge environment to low levels.
A method is also provided for maintaining a predetermined humidity level inside a cartridge for use in a data storage drive. This method includes: inserting the cartridge into a drive; engaging the media by opening the seal(s) of the first chamber and establishing mechanical, electrical, magnetic or optical connections with the media; actuating the linkage from the first chamber""s opening elements or a cartridge insertion detection alternative and using that actuation to engage the second chamber""s seal to close the opening of the second chamber and to protect the desiccant and pollutant getter from exposure to ambient; operating the drive; withdrawing the drive""s media connections; closing the first chamber from the ambient environment; triggering the actuator connected to the second chamber seal; and opening the second chamber to expose the data storage media to the desiccant and pollutant getter.
In an alternative embodiment, a method is provided to control the inside environment of a cartridge for protecting data storage media therein from a contaminant in the outside environment. The contaminant may include chemical pollutant, particulate or humidity levels outside the predetermined requirements of the media. As those skilled in the art will recognize, the contaminant may be either a chemical pollutant, particulate, or humidity or any combination thereof. This method includes: providing a closed cartridge with a first chamber for the data storage media and with a second chamber for material to control the contaminants in the inside environment in addition to openable closures for respectively selectively opening and closing the first chamber to ambient and the second chamber to the first chamber; opening at least one closure for connecting the first chamber to the ambient environment while accessing the data storage media; and opening at least one other closure when the one closure is closed to decontaminate the inside environment of any contaminant which entered the first chamber at least when the first chamber was open to ambient.
As those skilled in the art will recognize, the embodiments of this invention can vary depending upon the specific requirements of the data storage media, and the drive that operates upon the media. Accordingly, the particular size, shape and form of the cartridge, its chambers, seals, actuator, breather, desiccant, pollutant getters and the like may vary, depending on the particular application.
The above objects and other objects, features, and advantages of the present invention are more readily understood from a review of the attached drawings and the accompanying specification and claims.